# Reflection matrix causes twoSidedLighting material to be darker

**URL:** <https://forum.babylonjs.com/t/reflection-matrix-causes-twosidedlighting-material-to-be-darker/33700>\
**Category:** Bugs\
**Tags:** material\
**Created:** [September 6, 2022, 9:15am UTC](https://forum.babylonjs.com/t/reflection-matrix-causes-twosidedlighting-material-to-be-darker/33700 "2022-09-06T09:15:12Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Starryi](https://avatars.discourse-cdn.com/v4/letter/s/fbc32d/32.png) [@Starryi](https://forum.babylonjs.com/u/Starryi)\
**Post date:** [September 6, 2022, 9:15am UTC](https://forum.babylonjs.com/t/reflection-matrix-causes-twosidedlighting-material-to-be-darker/33700/1 "2022-09-06T09:15:12Z")

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> **[Babylon.js Playground](https://playground.babylonjs.com/#1YAIO7%23441)**
>
> Babylon.js playground is a live editor for Babylon.js WebGL 3D scenes

 ![截屏2022-09-06 17.07.03](https://us1.discourse-cdn.com/flex024/uploads/babylonjs/original/3X/a/4/a49fd563ae9563005f6544041fc836520ff8b4c1.jpeg)

All boxes’s material is PBRMaterial, and twoSidedLighting is set to be true.  
The blue one is transformed by reflection matrix, but is deeply darker than the red one.

because MirrorTexture uses ReflectionMatrix to implementing reflection, so the darker problem is also exists.

 ![截屏2022-09-06 17.13.08](https://us1.discourse-cdn.com/flex024/uploads/babylonjs/original/3X/c/2/c293906e20b0a1e474c73f5700ee40ae8e50cf2f.jpeg)

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<div class="post-metadata">

**Author:** ![carolhmj](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/carolhmj/32/25918_2.png) [@carolhmj](https://forum.babylonjs.com/u/carolhmj)\
**Post date:** [September 6, 2022, 3:29pm UTC](https://forum.babylonjs.com/t/reflection-matrix-causes-twosidedlighting-material-to-be-darker/33700/2 "2022-09-06T15:29:05Z")

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Hello! I’m not sure I understand your issue 🙂

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<div class="post-metadata">

**Author:** ![sebavan](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/sebavan/32/57_2.png) [@sebavan](https://forum.babylonjs.com/u/sebavan)\
**Post date:** [September 6, 2022, 7:03pm UTC](https://forum.babylonjs.com/t/reflection-matrix-causes-twosidedlighting-material-to-be-darker/33700/3 "2022-09-06T19:03:33Z")

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I would advise to disable `originBoxMat.useRadianceOcclusion = false;` in this case as it will mess up the use of normals in the mirror: [http://research.tri-ace.com/Data/cedec2011\_RealtimePBR\_Implementation\_e.pptx](http://research.tri-ace.com/Data/cedec2011_RealtimePBR_Implementation_e.pptx)

> **[Babylon.js Playground](https://playground.babylonjs.com/#1YAIO7%23446)**
>
> Babylon.js playground is a live editor for Babylon.js WebGL 3D scenes